Multiflash lamp unit

ABSTRACT

A DEVICE FOR THE SERIES IGNITION OF COMBUSTIBLE FLASHBULBS WHICH ARE ESSENTIALLY CONNECTED IN PARALLEL WITH ONE ANOTHER. EACH FLASBULB IS IN SERIES WITH A SWITCHING ELEMENT WHICH RESPONDS TO THE ENERGY EMITTED DURING FLASHING OF SAID FLASHBULB, AND PERMANENTLY INTERRUPTS THE ELECTRIC CONNECTION BETWEEN THE BULB AND THE CIRCUIT.

United States Patent 3,666,394 MULTIFLASl-l LAMP UNIT Johannes GerardusBok and Wilhelmus Polycarpus de Graaf, Emmasingel, Eindhoven,Netherlands, assignors to [1.5. Philips Corporation, New York, N.Y.

Filed May 18, 1970, Ser. No. 37,976 Claims priority, applicationNetherlands, May 30, 1969, 6908333 Int. Cl. F21k /02 US. Cl. 431-95 2Claims ABSTRACT OF THE DISCLOSURE A device for the series ignition ofcombustible flashbulbs which are essentially connected in parallel withone another. Each flashbulb is in series with a switching element whichresponds to the energy emitted during flashing of said flashbulb, andpermanently interrupts the electric connection between the bulb and thecircuit.

The invention relates to a multiflash lamp unit comprising photoflashlamps and an electric circuit in which the flashlamps are essentiallyconnected in parallel to one another and which flashlamps will beignited one at a time and one after the other each time the shuttermechanism is actuated.

Several types of multiflash lamp units for such series ignition areknown. A number of these units have in common that the currentconductors of the flashlamps are connected to the voltage source bymeans of the electric circuit across one or more switches one of whichcooperates with the shutter mechanism, which lamps remain connected orare connected to said voltage source when the next lamp is ignited, alsoafter they have been flashed.

It is found that this may cause difliculties in practice. It was foundthat the resistance between the current conductors after flashing isonly approximately 1 ohm in approximately 25% of the common photoflashlamps. This implies the formation of current bridges due to combustionproducts in the flashed lamp.

Common photoflash lamps are understood to mean flashlamps whereinignition means comprising two current conductors interconnected by afilament is present within a transparent envelope filled with acombustible metal wire filling and a combustion supporting gas such asoxygen or nitrofluoride/NF An ignition mass is provided on the terminalsof the current conductors which mass explosively burns after it hasreached a given temperature and thereby initiates the actinical reactionbetween the metal wire filling and the oxidizing gas.

The formation of current bridges does not only occur in this type oflamps, but also in so-called high-voltage photoflash lamp wherein theignition means comprises two current conductors which are electricallyconnected together within the bulb only by means of an ignition mass noignition filament being present. When applying a high voltage anelectric breakdown succeeded by a resistive heat development in theignition mass takes place upon which an explosive combustion of theignition mask starts and the actinical reaction between metal wirefilling and oxidizing gas is initiated.

If flashed lamps having a relatively low resistance between the currentconductors are present in an electric circuit including in-flashed lampssuch flashed bulbs completely or partly take up the supplied energy whenit is attempted to ignite one of the unflashed lamps. The result is thatnone of the in-flashed lamps, can be flashed under such circumstances.

This phenomenon particularly occurs when not all flashlamps in thecircuit are flashed one after the other. As is known cracks occur duringflashing in the envelopes of 3,666,394 Patented May 30, 1972 mostfiashlamps, which envelopes normally consist of glass. As a result thecontents of the envelope come in open communication with the atmosphere.Thus combustion products which initially do not conduct or conduct in anunharmful manner can become highly conducting due to attracting moisturefrom the atmosphere and can constitute current bridges between thecurrent conductors in flashed lamps.

The object of the present invention is to obviate these drawbacks. Tothis end a multiflash lamp unit provided with photoflash lamps which canbe ignited one after the other and are connected together in an electriccircuit is characterized in that each flashlamp is electricallyconnected in series to its own switching element which interrupts theelectric connection between at least one of the current conductors ofthe lamp and the circuit under the influence of the energy emittedduring flashing.

The switching element may consist of, for example, an electricallyconducting wire or strip incorporated in the circuit which wire or stripmelts under the influence of the energy emitted by the associatedflashlamp and permanently interrupts the electric connection between atleast one of the current conductors of this flashlamp connected inseries with the switching element and the circuit.

According to a preferred embodiment of the invention the switchingelement consists of a locally blackened wire or strip of an alloy ormetal preferably melting at a temperature of not more than 400 C. butmore than approximately C.

Metals suitable for this purpose are, for example, bismuth, cadmium,indium, lead, tin and alloys of these metals melting betweenapproximately 85 C. and approximately 400 C. and/or alloys of thesemetals and the metals silver, copper, zinc, aluminium, silicon,magnesium, antimony, nickel, thallium and gold.

Particularly suitable for the desired purpose is a strip of a knownsolder alloy of tin and lead (60:40) having a melting point of 180: Astrip having a section of 2 mm. x 0.014 mm. melts when it is at adistance of 15 mm. to 20 mm. from the wall of the envelope of a burningflashbulb and when it has been blackened by means of soot.

The switching element which is used according to the invention must ofcourse not be actuated by the energy which is emitted by a flashbulb notconnected in series with the switching element. If this condition andthe condition that the melting point of the material of which theswitching element consists, can be reached under the influence of theenergy emitted during flashing are satisfied the location of the elementdoes not further play an important role. The switching element may beprovided on the outer wall of the envelope or on or in the reflectoroperating with the flashlamp or in the vicinity of the base of theflashlamp, for example, on or in a holder for the flashlamp.

In order that the invention may be readily carried into effect, a fewembodiments thereof will now be described in detail by way of examplewith reference to the accompanying diagrammatic drawing, which showsthree systems for series ignition of combustible flashbulbs.

FIG. 1 relates to a multiflash lamp unit provided with high voltageflashlamps.

FIGS. 2 and 3 relate to units provided with common photo flash lamps.

FIG. 1 shows a principal circuit diagram of a circuit suitable forphotoflash lamps wherein ignition is induced by applying for a shortperiod a voltage which increases to a high value within a short time,for example, within several microseconds up to a value of severalthousands volts. Upon reaching the voltage value which corresponds tothe breakdown voltage of the flashlamp having the lowest breakdownvoltage in the multiflash lamp unit, this flashlamp is ignited. The nexttime when a flashlamp is to be ignited, the flashlamp which then has thelowest breakdown voltage of the unflashed lamps in the unit is ignited.

In the figure the reference numerals 1, 2 and 3 denote combustiblefiashlamps. More than three lamps may be present in the circuit. Eachlamp is connected in series through one of its current conductors 9 witha switching element 4 consisting of a locally blackened strip of aleadtin alloy (40:60) having a section of 1 mm. x 0.014 mm. Thefiashlamps 1 to 3 are mutually connected in parallel by means of thecurrent conductors 7 and 8. The lamps are connected by means of theseconductors to a high voltage source, not shown, which supplies a voltageincreasing to a high value within a short period when the shuttermechanism of the camera is actuated. The current conductors 9 and 10 ofthe fiashlamps are connected within the envelope by an ignition masscomprising a mixture of zirconium powder and potassium perchlorate andfurthermore the mixture comprises approximately 30 vol. percent ofapproximately 1% by weight of strontium containing lanthanum cobaltitewhich is a semiconducting material and a binder. The fiashlamps containzirconium wire filling 5 and oxygen. When flashing a lamp the strip 4which is located at a distance of approximately 5 mm. from the wall ofthe envelope of the lamp melts, so that the connection between the lampand the current conductor 8 is completely and permanently interrupted.Each lamp has its own reflector (diagrammatically shown by broken linecircles 11) which may also be used to shield the switching element 4from irradiation by flashbulbs not associated therewith.

FIG. 2 shows a principal circuit diagram of a circuit suitable forcommon fiashlamps provided with an ignition filament connecting thecurrent conductors within the envelope and an ignition mass in thevicinity of said filament. This ignition mass comprises, a mixture ofzirconium powder, potassium perchlorate and a binder (29).

The circuit includes the fiashlamps 21, 22 and 23. The circuit is notlimited to this number. The lamps 21, 22 and 23 are series-arranged withswitching elements 24 which upon flashing of the fiashlamps interruptthe connection between the relevant flashlamp and the current conductor25 under the influence of the emitter energy. The flashlamp 22 and 23are also series-arranged with a switching element 27 which upon flashingof the previous lamp establishes the electrical connection between thenext flashlamp and the current conductor 26. The switching elements 27are provided in the system in such a manner that they can only beoperated by a previous flashlamp, for example, by accommodating thempossibly jointly with the switching element 24 in the reflectors(diagrammatically denoted by the broken line circles 28). Furthermorethe fiashlamps are connected by means of the current conductors 25 and26 to a device, not shown, which provides a current during a shortperiod when the shutter mechanism of the camera is actuated. Suchdevices are known to the art. If flashlamp 21 is ignited, the connectionbetween this lamp and the current conductor 25 is interrupted and theconnection between flashlamp 22 and the current conductor 26 isestablished.

FIG. 3 shows a principal circuit diagram of a circuit which is suitablefor common fiashlamps wherein the fiashlamps are essentially connectedmutually in parallel and in series with resistors the resistances ofwhich increase in the sequence of ignition.

The reference numerals 31 to 34 denote fiashlamps of the common typewherein the current conductors 35 and 36 are interconnected within theenvelope of the flashlamp by means of a filament 37. The envelopefurthermore contains zirconium wire filling 79 and oxygen. Thefiashlamps 31 to 34 are connected across switching elements 38 to 41 tothe current conductor 42, and the fiashlamps 32 to 34 are connectedacross resistors 43 to 45 to the current conductor 46. The resistance ofthe resistor 45 is then higher than that of the resistor 44 and theresistance of the resistor 44 is in turn higher than that of theresistor 43. The mutual ratio of the resistances may, for example,always be chosen to be 2:1 in the given sequence.

The circuit can be connected by means of the current conductors 42 and46 to a device not shown which supplies current during a short periodwhen the shutter mechanism of the camera is actuated; such devices areknown to the art.

Each flashlamp has its own reflector (diagrammatically shown by thebroken line circles 47) which may also be used to shield the switchingelements 39, 40 and 41 from irradiation by a previously flashed lampwhich is not series-arranged with the switching element.

If a current is applied to the circuit by means of the previouslymentioned device, flashlamp 31 is first ignited and the connectionbetween the current conductor 35 and the current conductor 42 isinterrupted by the switching element 38 under the influence of theemitted energy. The next time when a current is applied to the circuit,flashlamp 32 is ignited and the switching element 39 interrupts theconnection between the current conductor 48 and the current conductor 31under the influence of the emitted energy.

The relative magnitudes of the resistances have been chosen to be suchthat the combustible fiashlamps ignite in the given sequence and thattwo or more fiashlamps are not simultaneously ignited.

The switching elements 38 to 41 may comprise a strip of a lead-tin alloy(40:60) as mentioned in the previous example.

The present invention provides a simple and reliable, yet inexpensivestep by which these drawbacks relating to the use of circuits for seriesflashing wherein fiashlamps are essentially connected in parallel can besurmounted, which drawbacks consist in the circuit not furtherfunctioning it one of the fiashlamps has a relatively low resistanceafter flashing.

What is claimed is:

1. In a multiflash lamp unit sequential ignition of fiashlamps of thetype having a plurality of fiashlamps connected in parallel with eachother and means to sequentially ignite said fiashlamps wherein theimprovement comprises a plurality of switching elements included in saidsequential ignition means, each of said switching elements being inseries with a corresponding flashlamp for interrupting the ignitingmeans for said fiashlamp after said flashlamp is ignited, said switchingelements comprising an electrically conducting, locally blackened stripof material having a melting point between substantially C. and 400 C.,said strip of material further being positioned in the vicinity of saidflashlarnp.

2. A unit as claimed in claim 1 wherein said material is selected fromthe group consisting of bismuth, cadmium, indium, lead, tin, and leadtin (40:50) alloy.

References Cited UNITED STATES PATENTS 3,443,875 5/1969 Herrmann 431-3,459,487 8/1969 Glenn 43l95 3,518,487 6/1970 Tanaka et a1. 431-95 X3,532,931 10/1970 Cote et al 431 9s X FOREIGN PATENTS 1,192,047 4/ 1965Germany 431-95 EDWARD J. MICHAEL, Primary Examiner 753? UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3666394 Dated May 13,1972 I en (s) JOHAN'NES GERADUS BOK ET AL It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 4, line 27, "31" should read -42- Column 4-,. line 59, (4-0 :50)should read (40:60)

Signed and sealed this 5th day of September 197-2.

(SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M.FLETCHER,JR.Attesting Officer

